3D video is becoming popular in consumer electronics. This is largely due to the increasing popularity of 3D cinema. However none of the existing implementations of 3D video are completely satisfactory. One popular approach, using time sequencing of the left and right images, employs active shutter glasses to extract the stereo image out of the time domain. One problem with this approach is that each eye sees light only half of the time, leading to a diminished perceived brightness. Another problem is that the active shuttering can lead to the perception of flicker in the image which can result in eye fatigue or other physical symptoms. In order to eliminate flicker, the imagers must be operated at high frequencies in order to blur out the modulation. This increases the technical requirements and cost of the imagers. In addition, the active shutter glasses can be quite expensive and are generally not suitable for large audiences.
A second approach, popularized by Real-D Cinema Systems, is to use polarized light to present two different images to the eyes, one polarization for the left eye and a second polarization for the right eye. In the Real-D approach, the light is circularly polarized in order to minimize the impact of rotations of the face around the viewing axis. One advantage of the Real-D process is that it uses passive glasses, and the lenses of the glasses need only be circularly polarized in an opposite sense to one another. Typically in the Real-D process, either two separate projectors are used and the outputs separately circularly polarized, or a single projector is used and in a time sequential manner the output is polarized with alternate circular polarizations. One disadvantage of the Real-D system is that half of the light is lost: in the first case two projectors are required, but one polarization from each is discarded, and in the second case half of the light is lost when one polarization is discarded in a time sequential fashion.
A third approach, by Dolby Laboratories and others, uses two sets of additive primary colors, one for each eye to create the stereo image. A set of passive glasses, each lens of which transmits only the appropriate set of additive primaries is provided to separate out the stereo images for the viewer. One disadvantage of this approach is that the optical efficiency can be rather low, or the complexity of the projector is rather high.